Bodyweight Regulation: Leptin Part 2

In the Bodyweight Regulation: Leptin Part 1, I talked primarily about leptin (and a bit about insulin,and a very little bit about the other hormones) and its discovery and how it may be the (or at least one of the) long-sought after hormones involved in regulating bodyweight. Today I want to take a quick look at what leptin is and how it’s regulated. Next time I’ll look at what leptin is doing (or not doing as the case may be).

Leptin is a protein hormone released primarily from fat cells although skeletal muscle, the gut and possibly the brain releases it too. But, in terms of overall quantity, fat cells are the primary place where leptin is synthesized and released.

Quite in fact, leptin scales scarily well with body fat percentage, as I noted on Wednesday, primarily with subcutaneous body fat percentage. The higher the level of body fat, the higher the leptin level and vice versa. Males below 10% body fat may have no detectable leptin in their bloodstream.

Tangentially, I suspect that this may be part of what’s involved in terms of why women generally have a harder time losing fat (a topic I discussed in some detail in my Bromocriptine booklet and that I’m delving even more heavily into right now).

However, leptin doesn’t only scale with body fat percentage, it is also related heavily to food intake, specifically carbohydrate metabolism in the fat cell.

When someone starts a diet, leptin may drop by 30-50% within about a week, obviously they haven’t lost that much of their body fat. After that rapid initial drop, drops in leptin are much slower scaling with body fat loss.

By the same token, with even short-term overfeeding, leptin can come up far more quickly than body fat is gained. This latter fact is part of the basic premise behind refeeding and cyclical dieting; short-term very high carbohydrate/caloric intakes can raise leptin without causing significant fat gain.

This is why my diets always base refeeds around periods of high-carbohydrate intakes, acutely this is the only way to affect leptin levels in the short-term.

In essence, leptin is telling your body two different things:

1. How much fat you’re carrying.

2. How much you’re eating.

From the standpoint of bodyweight regulation and physiology, these are important things for the body to know about.

I want to note again that, as I mentioned in the last post, insulin is also a player in bodyweight regulation, scaling primarily with visceral fat and there is evidence that men’s and women’s brains are relatively more or less sensitive to the two hormones.

I’d mention that, from a practical standpoint (regarding refeeds), this doesn’t particularly matter in that both leptin and insulin will primarily be increased via high-carbohydrate refeeds.

In any case, leptin (and insulin and, of course, the other hormones I mentioned last time) are sending a signal to the brain about body fat levels and food intake, making them likely candidates for bodyweight regulation. So how are they working exactly?

That’s what I’ll talk about next time (still focusing on leptin but starting to address some of the other hormones as well).